1. Field of the Invention
This invention relates to a method of cutting out blanks from flat, irregular workpieces, in particular leather pieces, in which the contour and the flaws of the workpieces spread on the supporting surface of an imaging arrangement are optically detected by a camera, where the flaws of the workpieces and preferably other workpiece-own features characteristics of the workpieces are marked manually, and the markings together with the contour and a workpiece identifier are detected and the corresponding data are entered into a computer, then on the basis of these data and the data stored in the computer as to number, design and quality requirements of the blanks a pattern is prepared by the computer for each workpiece and stored in allocation to the respective workpiece, where the detected workpiece identifier of a workpiece is used as workpiece identification for the allocation of the computed pattern, whereupon the workpieces are cut by a cutting means that can be activated by the computer in accordance with a control program taking into account the allocated patterns.
When industrially cutting out blanks from leather pieces or other irregular flat pieces, it is not only desired to achieve an optimum utilization of material, but also an economic nesting, where nesting is understood to be a combination of the various blanks to form a pattern individually adjusted to the respective workpiece. Since in such nesting, the flaws of the workpieces such as holes, surface structure and color, stretching direction or the like must of course be taken into account, an optimization of the utilization of material mostly involves an increase in care and time required for nesting.
2. Description of the Prior Art
For automating this nesting it is known in accordance with and U.S. Pat. No. 4,725,961 to digitize the contour of the workpiece by means of a computer and display the same on the screen of a layout unit, so that on the screen an interactive nesting can be performed by an operator by means of stored blank shapes. However, both for digitizing and for cutting the workpiece must remain on the same supporting surface of a working table, there will be long nesting times, and since flaws are detected only due to digitizing, the nesting result remains unsatisfactory.
In accordance with the U.S. Pat. No. 4,982,437 and the DE-A-41 11 304 as well as the U.S. Pat. No. 5,089,971 it is also already known to manually mark the flaws of a workpiece and optically detect the contour and the manual markings and enter the corresponding data into a computer for preparing the pattern, where the DE-A-41 11 304 and the U.S. Pat. No. 5,089,971 already propose to separate the nesting and cutting operations and also use the detected workpiece identifiers of a workpiece as workpiece identification for the allocation of the computed pattern for the cutting operation. It is, however, necessary to place the workpieces to be cut on the working surface of the cutting means in a position exactly corresponding to the position for the optical detection in the imaging arrangement, which mostly requires separate workpiece supports for the workpieces, which in adjusted positions can be mounted both on the supporting surface of the imaging arrangement and on the working surface of the cutting means. In addition, it is also possible to indicate the correct position of the workpiece on the working surface of the cutting means by a projection of the workpiece contour activated by the computer, so as to achieve the required allocation between workpiece and control program stored in the computer and predetermined by the pattern. Handling the workpieces by means of separate workpiece supports or properly positioning the workpieces on the cutting table in accordance with predetermined projections, however, involves a considerable amount of time and effort and endangers the quality of the cutting operation through an incorrect position of the workpieces on the working surface of the cutting means.